胎先露下降受阻的原因，错误的是（）。
A.骨盆狭窄
B.子宫收缩乏力
C.胎位异常
D.胎头过大或胎儿畸形
E.胎膜早破
参考答案：E
加热炉辐射室及对流室有何作用？
Precedence Diagramming Method (PDM) is a method used in activity sequencing．There are four types of dependencies or precedence relationships in PDM．The initiation of thesuccessor activity depends upon the completion of the predecessor activity is called ______．
A．Finish-to-Start
B．Finish-to-Finish
C．Start-to-Start
D．Start-to-Finish
